By any accounts Clifford Curtis is an intelligent man. He completed high school at age 16, and later became an engineer and an attorney.

So his daughter Laura was shocked when she noticed a Western Union receipt indicating her 83-year old dad had wired some unknown person $3,000.

"Then we started seeing more receipts," she told ABC News, "and panic set in."

Curtis was sending the money to collect his lottery winnings. At least that's what he thought. He'd received calls telling him he had won a foreign lottery. All he had to do was pay fees and taxes and the millions would be his.

"The phone would ring all day," Laura Curtis said. "It was those scammers telling him he'd won money. Then the mail started, we got over 300 pieces of mail a week once his name was out there."

The elderly Washington State man had fallen victim to an increasingly common scam. "There is just no question that this is really massive, and it really hits older consumers," said C. Steven Baker, director of the Federal Trade Commission's Midwest Region.

The FTC estimates that Americans are losing $1 billion a year to foreign lottery scams.

The U.S. Postal Service is so concerned that it teamed up with AARP and this week sent out 25 million mailers to older Americans, warning them to be on guard.

"Jamaica is the latest hot spot," said Paul Krenn, Assistant Inspector-in-Charge for the U.S. Postal Inspection Service.

So many scam artists are promising unsuspected Americans that they've won the Jamaican lottery, that officials are warning don't even answer phone calls from Jamaica's 876 telephone prefix.

There have been victims in 21 states, according to the U.S. Senate Committee on Aging, which will hold a hearing on this type of fraud next week.

"All foreign lotteries are scams," said Doug Shadel, a former fraud investigator who now heads ups AARP's Washington State office. "It's illegal to participate in foreign lotteries, so that is the biggest red flag." He added,
"Anytime anyone tells you you've won something and …you have to pay a fee, it's a scam, period."

Laura Curtis said the fraud artists were so convincing, that her father was sure he'd won. They'd even invoke the name Publisher's Clearing House, or Prize Patrol. Those fleecing her dad were relentless. "The invaded his whole life, they would start calling at 4 a.m. and wouldn't stop until midnight."

Curtis broke down as she talked to ABC about the ordeal, which went on for over a year until she and her siblings were able to get the courts to declare her father incapacitated so he no longer had access to his bank accounts.

The family tried everything to try to put stop the scammers. "We cut the phone lines, we changed the phone numbers, and they'd always find him. We finally had to cut the phone lines, physically cut it with a scissors to stop the calls."

By that time, Clifford Curtis had handed over $180,000 to try to collect his supposed lottery winnings.
With the help of postal inspectors,
his children were able to recover just two packages totaling $17,000.

The AAPR's Shadel says big losses are not uncommon. "We've seen people lose $300,000, $400,000. And you might say to yourself, well they must be rich, so they can afford to lose that money. No, that's ALL of their money."

The group has a nationwide Fraud Fighter Call Center (1-800-646-2283) for victims, or for those who want to question whether an solicitation they've received is fraudulent.

AARP says the most common victims of lottery scams are over age 70, often women, and with lower incomes and education levels. Yet as the Curtis case shows, it can happen to anyone. "People think this only happens to dumb and senile people," said the FTC's Baker. "I can tell you that's not true."

Those behind the frauds are difficult to catch. They are operating outside the U.S., and making untraceable calls over computer networks. The money is almost never recovered. "Once it [the money] is picked up, it's gone," said Baker.

In their mailing this week to consumers, the U.S. Postal Service and AARP warn that if something sounds too good to be true, it is. They urge consumers who are contacted about winning a foreign lottery to hang up, ignore emails and throw out any letters.

One you're drawn in, it's difficult to get out. "These guys will call you 40 to 50 times a day. They will leave threatening messages. They will tell you they're watching you on Google satellite to scare you," said the AARP's Shadel.

The harassment and pressure devastated the Curtis family, according to Laura. She is convinced the stress hastened her father's mental decline. "It is so overwhelming at times to think about it," she said, "Once you are a victim, it is almost impossible to get away from it."